Aluminum alloys



Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE ALUMINUM ALLOYS Walter A. Dean and Louis W. Kempf, Cleveland,

Ohio, America, Pittsburgh, Pennsylvania assignors to Aluminum Company of Pa., a corporation of No Drawing. Application September 21, 1932 Serial No. 634,165

3 Claims.

mon impurities found in commercial aluminum.

A good foundry alloy which will retain a substantial proportion of its physical and tensile properties at elevated temperatures is constantly being searched for in the field of light metals. By light metals are not meant the ordinary aluminum base alloys but only such of those alloys as contain substantial amounts of a metal lighter than aluminum so as to compensate in the alloy for the addition of metals heavier than aluminum. To provide such an alloy of good foundry characteristics and excellent strength at high temperatures is the object of this invention.

The aluminum base alloys containing magnesium are lighter than aluminum. They should therefore be excellent material from which to manufacture reciprocating parts which operate at elevated temperatures were it not for the fact nesium, 0.5 to 4.0 per cent by weight of manga nese, 0.5 to 4.0 per cent by weight of nickel, and 0.5 to 4.0 per cent by weight of copper, the balance being principally aluminum. This alloy, we have discovered, has very good foundry characteristics, being capable of use either in sand or permanent molds. The alloy is light, is strong and hard and possesses these latter properties to a substantial extent at high temperatures. The alloy is, moreover, stable in its properties over long periods at high temperature and is therefore a very dependable engineering material.

Also the alloy is insensitive to impurities, which is to say that its properties are not materially affected by the varying amount of impurities, such as iron, which may be found in the commercial aluminum from which it is usually made.

The tensile strength of the alloy is high at elevated temperature and its elongation, while not as high as might be desired, is adequate when ductility is not a leading property. Examples of the strength and ductility of the alloys will be found in Table I where are listed the tensile strength and elongation of two sand castings made of the alloy, annealed for 4 hours at 700 Fahrenheit, cooled to 600 Fahrenheit, and finally tested at the latter temperature.

Table I Alloy composition Tensile strength pounds persquare inch Percent elongation in 2 inches For comparison it may be stated that a binary aluminum-magnesiumv alloy containing 6 per cent magnesium and in sand cast form had, after a similar thermal treatment, a tensile strength of only 15,000 pounds per square inch and an elongation of 5 per cent in 2 inches.

The superior strength of our new alloys at elevated temperatures may be shown by comparison of one of the alloys in sand cast form with a sand casting made of a well known chromium alloy containing copper. Sand castings made of an alloy containing 6 per cent magnesium, 1.0 per cent manganese, 1.5 per cent nickel, and 2.0 per cent copper, balance aluminum, were annealed for 4 hours at 700 Fahrenheit, the temperature was then reduced to 600 Fahrenheit and the alloys tested at that temperature. Similar treatment was afforded sand castings made of an alloy containing 10 per cent copper, 0.2 per cent magnesium, 1.2 per cent iron, balance aluminum, and these castings were similarly tested. The results are shown in Table II.

Tensile 7 Strength gi i pounds g3 Alloy Composition tion per in 2 1 35 inches 6%Mg 1.0% Mn 1.5% Ni 2.0% Cu 20,000 1.0 10% Cu 0.2%Mg 1.2% Fe 15,300 2.0

The aluminum-magnesium-manganesenicke1- copper alloys to which this invention refers have certain preferred forms. Within the composition limits above described, the alloys are satisfactory for most purposes, but we have found the best combination of properties in alloys containing 3.5 to 6.5 per cent by weight of magnesium, 0.5 to 2.0 per cent by weight of manganese, 0.5 to 3.0 per cent by weight of nickel, and 1.0 to 2.5 per cent by weight of copper, balance principally aluminum. The addition of very small amounts of antimony and bismuth (which metals may be regarded as a class) exerts a remarkable effect upon the properties at high temperatures. We have discovered that when' about 0.05 to 0.4 per cent by weight of these metals, singly or together (but in total amount not exceeding 0.4 per cent) is added, the ductility of the alloys is materially increased at elevated temperatures. However, larger amounts of antimony and/or bismuth have the opposite efiect and are detrimental to the alloy.

The alloys which are herein described may be made by any of the usual methods of compounding alloys, care being taken, of course, not to overheat or dross the metal during alloying.

Another property of these alloys is their improved fluidity as compared with the alloys which have, heretofore, been widely used as a material for parts operating at elevated temperatures. Comparative tests, based upon the distance that the molten alloy, originally heated to a given temperature, will flow through a spiral formed in a sand mold, have shown that our novel alloys are very superior with respect to fluidity.

The aluminum used in the manufacture of the alloys may be of the highest purity or it may contain amounts of usual impurities, and the term aluminum as used herein and in the claims-designates the aluminum of commerce. It is an incidental property of our alloys that the presence of iron in amounts as high as 2 percent by weight is not harmful to the high temperature properties of the alloys and, therefore, a wide choice between the various grades of commercial aluminum is possible.

We claim:

1. A metallic alloy consisting of 3.0 to 8.0 per cent by weight of magnesium, 0.5 to 4.0 per cent by weight of manganese, 0.5 to 4.0 per cent by weight of copper, 0.5 to 4.0 per cent by weight of nickel, and 0.05 to 0.4 per cent by weight of at least one of the class of elements antimony and bismuth, the total amount of the antimony and/or bismuth being not greater than 0.4 per cent by weight, the balance being substantially aluminum.

2. A metallic alloy consisting of 3.5 to 6.5 per cent by weight of magnesium, 0.5 to 2.0 per cent by weight of manganese, 0.5 to 3.0 per cent by weight of nickel, 1.0 to 2.5 per cent by weight of copper, and 0.05 to 0.4 per cent by Weight of at least one of the class of elements antimony and bismuth, the total amount of the antimony and/or bismuth being not greater than 0.4 per cent by weight, the balance being substantially aluminum.

3. A metallic alloy consisting of 6.0 per cent by weight of magnesium, 1.0 per cent by weight of manganese, 1.5 per cent by weight of nickel, 2.0 per cent by weight of copper, and 0.05 to 0.4 per cent by weight of at least one of the class of elements antimony and bismuth, the total amount of the antimony and/or bismuth being not greater than 0.4 per cent by weight, the balance being substantially aluminum.

WALTER A. DEAN. LoUIs w. KEIVIPF.

CERTIFICATE OF CORRECTION.

Patent No. 1, 932, 847.

October 31, 1933.

WALTER A. DEAN, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring "chromium" read aluminum; and this correction therein that the in the Patent Office.

Page 1, line 82, for

Signed and sealed this 5th day of December, A. D. 1933.

(Seal) t. M. iiopirini Acting Commissioner of Pate-m8. 

